JPH0354812Y2 - - Google Patents

Description

[Detailed Description of the Invention] (Industrial Application Field) The present invention relates to a holder used for attaching a rotary cutting tool such as a drill or tap to the main shaft of a machine tool.

(Prior Art) Rotary cutting tools such as drills have a reduced cutting performance due to wear of their blades and an increase in cutting torque. Therefore, the timing of re-sharpening of drills, etc. is determined by determining the number of pieces to be processed, but it is difficult to manage the lifespan when the workpiece material and cutting conditions change, and the workpiece may break during cutting, resulting in defective workpieces. There are many cases where Small-diameter drills and taps are particularly prone to breakage, and they often break easily even when chips become clogged during cutting.

A sensor that captures ultrasonic vibrations when a tool breaks is known as a means of detecting tool breakage during cutting, but what is actually necessary is to stop the machine before the tool breaks. , to replace the tool.

The main reason why a rotary cutting tool breaks is that the cutting torque increases due to wear of the blade or clogging of chips, as mentioned above. We thought that rotating the tool via a safety clutch would prevent the tool from breaking, and for example,
As described in the above publication, it has been considered to interpose a ball clutch that slips when a certain torque is exceeded between the spindle that holds the tool and the holder body.

(Problem to be solved by the invention) However, with conventional holders, when the cutting torque exceeds a certain value, even though the ball clutch can automatically cut off the transmission of rotational force to the tool, the rotational force in the axial direction Since the feeding continues, the tool is compressed in the axial direction, and the increased compressive stress causes the tool to break. In particular, small-diameter drills, taps, etc. may easily buckle and fail due to increased compressive stress in the axial direction. That is,
As mentioned above, simply interposing a safety clutch between the spindle that holds the tool and the holder body has not been able to reliably prevent tool breakage.

Furthermore, it is not possible to electrically detect an abnormal situation in which the safety clutch is activated and automatically control the machine tool.

(Means for Solving the Problems) In order to solve the above-mentioned conventional problems, the present invention has been developed by attaching a spindle with a tool chuck at the tip to a holder body having a shank part for attaching to a machine tool. The holder body is supported concentrically so as to be able to rotate around the center and move in the axial direction within a certain range, and between the holder body and the spindle, the spindle is biased and held at the limit position. At the same time, a clutch is provided which slips when the torque exceeds a certain level, and an electrical insulating part is provided to electrically insulate the spindle and the shank part, and the spindle is moved backward from the extension position against the force. The present invention proposes a rotary cutting tool holder which is provided with a switch means that occasionally contacts the spindle and the shank portion to establish electrical continuity between the spindle and the shank portion.

(Operation of the invention) The shank portion of the tool holder is set on the main shaft of the machine tool, and a rotary cutting tool such as a drill is attached to the tool chuck to perform cutting work, and the tool is held through the tool chuck. The spindle is coupled to the holder body via the clutch at an end position relative to the holder body. Therefore, by setting the maximum transmission torque of the clutch so that the clutch slips at a rotational force slightly lower than the limit cutting torque that is balanced with the torsional breakage strength of the tool, the blade part can be adjusted to the allowable limit. If the cutting torque exceeds the transmission torque of the clutch due to excessive wear or clogging, the holder body will idle relative to the spindle (tool) due to the action of the clutch. That is, it is possible to prevent a torsional stress exceeding the torsional breakage strength from acting on the tool due to excessive cutting torque.

After the clutch operates and the forced rotational drive of the spindle (tool) stops as described above, even if the holder body moves forward in the direction of the rotation axis due to the feed of the main shaft, the biasing force that holds the spindle at the limit position Only the holder main body moves in the direction of the rotational axis relative to the spindle (tool) against this, preventing excessive axial compressive stress that exceeds the compressive breakage strength from acting on the tool. It is possible.

At this time, the spindle moves backward relative to the holder body, so that the switch means comes into contact and the spindle and the shank portion of the holder body are electrically connected. As a result, the main shaft of the machine tool, the shank part of the holder body, the switch means, the spindle, the rotary cutting tool,
An electrical closed circuit is formed through the conductive workpiece and the machine tool body. The formation of this electrical closed circuit means that, for example, as in the contact detection device between a tool and a workpiece described in JP-A No. 61-214953 and JP-A-54-49691, when the electrically closed circuit is loosely fitted into the main shaft, This can be easily detected using a sensor, and based on this detection result, for example, the spindle is pulled back and automatically stopped. The spindle is fed again after being pulled back once, and when the spindle has reciprocated a set number of times, the spindle is stopped at the pulled back position.The tool holder of the spindle that has stopped at the pulled back position is replaced with a new tool as a spare tool. The machine tool can be automatically controlled by an arbitrary program, such as starting cutting again after automatically replacing the holder with an automatic tool changer.

(Effects of the invention) As described above, according to the tool holder of the invention,
Not only can it prevent the cutting torque acting on the rotary cutting tool from exceeding a certain value, but it can also prevent excessive compressive force from acting on the tool, so it can prevent twisting caused by excessive cutting torque of the rotary cutting tool. This makes it possible to reliably prevent buckling and breakage due to excessive compressive force in the axial direction.

Also, by using a switch means that closes the situation in which the built-in clutch is activated by subsequent relative movement in the axial direction between the spindle and the holder body,
Since it can be reliably detected using a conventionally well-known simple method, it is possible to carry out various automatic controls as described above based on the detection results, and to take reasonably necessary measures. Moreover, instead of having a special control signal transmitting device that requires a power source built into the holder, the holder simply has a built-in switch that operates in conjunction with the spindle, which simplifies the internal structure of the holder and allows it to be used in large numbers. It is possible to reduce the cost of the holder.

(Example) An example of the present invention will be described below based on the attached illustrative drawings.

In Fig. 1, 1 is the holder body, and the shank part 3 serves as the attachment part to the main shaft 2 of the machine tool.
and a cylindrical main body 6 concentrically attached to the outer end of the shank portion 3 with an electrically insulating material 4 by bolts 5. A spindle 7 is supported concentrically within the cylindrical body 6 by a pair of front and rear rotary bearings 8a and 8b, and has a tool chuck 9 at its outer end protruding from the cylindrical body 6. The spindle 7 is rotatable around the axis relative to the cylindrical body 6 by the rotary bearings 8a and 8b, and at the same time there is a small gap (fitting tolerance) between the rotary bearings 8a and 8b. can be moved in the axial direction. The minute distance between the spindle 7 and the rotation bearings 8a, 8b
Since an oil film of lubricating oil is present therein, the spindle 7 can be supported with high precision in a state where it can move in the axial direction. Further, the spindle 7 and the shank portion 3 are electrically insulated by an electrically insulating portion 10 made of the electrically insulating material 4.

11 is a ball clutch, and as shown in FIGS. 1 and 2, a ball support plate 12 integrally protrudes from the spindle 7,
a ball support groove 13 formed radially inside the
A ball 14 is partially fitted into each ball support groove 13 so as to be movable in the radial direction relative to the spindle 7, and a ball presser is loosely fitted to the spindle 7 inside the ball support plate 12 so as to be movable in the rotational and axial direction. Board 1
5. A compression coil spring 16 that presses the ball pressing plate 15 toward the ball supporting plate 13, and a compression coil spring 16 provided on the cylindrical inner circumferential surface 6a of the cylindrical body 6 so that a portion of each ball 14 fits therein. It is composed of a plurality of ball locking holes 17 in the circumferential direction.

The ball pressing plate 15 urged by the spring 16 presses each ball 14 with its conical pressing surface 15a. As a result, the spindle 7 is urged outward in the axial direction via the ball support plate 12, so that the spindle 7 is held at the limit position where the ball support plate 12 abuts the rotary bearing 8a. On the other hand, the conical pressing surface 1 of the ball pressing plate 15
5a biases each ball 14 in the centrifugal direction with respect to the spindle 7, so when the spindle 7 is at the limit position as described above, a portion of each ball 14 engages with the ball on the cylindrical body 6 side. They fit into the stop holes 17, respectively. In other words, the clutch is engaged.

Reference numeral 18 denotes a transmission torque adjusting means, which, as shown in FIGS. 1 and 3, is loosely fitted onto the spindle 7 so as to be relatively movable in the axial direction and receives the inner end of the spring 16, and a spring receiving plate 19 which receives the inner end of the spring 16; The cylindrical main body 6 is arranged so that the two protrusions 19a protruding from the spring receiving plate 19 in the diametrical direction pass through each of the protrusions 19a.
Two elongated holes 20 which are long in the axial direction are provided in the cylindrical body 6, and the two protrusions 19a are fitted into the inner circumferential surface of the cylindrical main body 6. It consists of an adjustment ring 23 with a mating annular groove 22 and a lock bolt 24 of the adjustment ring 23. Note that 25 is a transmission torque display scale provided on the outer peripheral surface of the cylindrical main body 6.

The state shown in FIG. 1 is a state in which the spring receiving plate 19 is retracted to the maximum retraction position by the adjustment ring 23, and the initial compressive stress of the spring 16 is minimized, that is, the transmission torque of the ball clutch 11 is adjusted to the minimum. Indicates the condition. Therefore, when increasing the transmission torque of the ball clutch 11, loosen the lock bolt 24 and adjust the adjustment ring 2.
3 in the drawing-out direction, and the spring receiving plate 19 is moved forward in the axial direction via the protrusion 19a in contact with one side of the annular groove 22, thereby compressing the spring 16. That is, by rotating and letting out the adjustment ring 23, the ball clutch 11
The transmission torque of the ball clutch 11 becomes larger, and the rotational pullback of the adjustment ring 23 causes the transmission torque of the ball clutch 11 to become smaller.

Reference numeral 26 denotes a switch means, which includes a movable switch piece 27 fitted to the inner end of the spindle 7 so as to be movable in the axial direction within a certain range, and a movable switch piece 27 that is biased and held at the limit position. and a contact surface 29 formed inside the shank portion 3 so that the tip contact portion 27a of the movable switch piece 27 contacts when the spindle 7 moves backward.

When in use, the shank portion 3 of the holder body 1 is attached to the main shaft 2 of a machine tool in the same way as a conventional tool holder, as shown by the imaginary line in FIG. 1, and the required rotary cutting tool,
For example, attach a drill T. The transmission torque of the ball clutch 11 is adjusted by the adjustment ring 23 as described above so that the rotational force or axial thrust that exceeds the breakage strength of the drill T does not act on the spindle 7.

The holder main body 1 and the spindle 7 are connected in the rotational direction and the axial direction by the ball clutch 11 which is in a transmission state with a part of the ball 14 fitted into the ball locking hole 17.
When the main spindle 2 is rotated and fed in the axial direction, the main spindle 2, holder body 1, spindle 7, and drill T rotate together and move forward in the axial direction, and the workpiece is machined by the drill T. The object W can be cut and punched.

During this cutting and drilling process, the cutting torque acting on the spindle 7 is transmitted to the ball clutch 11 due to clogging of chips in the cutting hole or wear of the blade of the drill T exceeding the limit. When the torque is exceeded, the force of the spring 16 that causes the ball 14 to fit into the ball locking hole 17 via the ball pressing plate 15 is overcome by the force of the periphery of the ball locking hole 17 pushing out the ball 14, and the spindle While the holder body 1 (cylindrical body 6) rotates relative to the ball 7 in the circumferential direction, the ball 14 is pushed out from the ball locking hole 17 as shown in FIG. At this time, the ball 14 rolls in the ball support groove 13 in the centripetal direction while pushing away the ball pressing plate 15 against the biasing force of the spring 16, and is released from the ball locking hole 17. It rolls on the columnar inner peripheral surface 6a in the rotational circumferential direction. As a result,
It is possible to prevent the cylindrical body 6, that is, the holder body 1 from rotating idly with respect to the spindle 7, and the application of excessive cutting torque that would cause twisting and breakage of the drill T.

As mentioned above, even after the rotational force transmission from the holder body 1 to the spindle 7 is cut off by the action of the ball clutch 11, the holder body 1 continues to rotate and move forward in the axial direction due to the rotation and feeding action of the main shaft 2. However, since the holder main body 1 and the spindle 7 are movable relative to each other in the axial direction with sliding between the rotary bearings 8a, 8b and the spindle 7, Only the main body 1 rotates and moves forward in the axial direction, and the drill T is compressed in the axial direction by simply compressing the spring 16 of the ball clutch 11 via the spring receiver 19 that moves forward together with the holder main body 1. There is no need to apply excessive axial compressive force that would cause breakage. Note that the ball 14 pushed out from the ball locking hole 17 at this time is
As shown in the figure, the cylindrical inner peripheral surface 6a of the cylindrical main body 6
While rolling in the circumferential direction of the rotation, it also rolls in the direction of the rotation axis.

The ball clutch 11 is a means for transmitting rotational force from the holder body 1 to the spindle 7 as described above, and at the same time is a means for transmitting thrust in the axial direction. Even when the cutting rotational force is being transmitted, if an excessive axial reaction force acts on the spindle 7, the spring 16 will move against the ball pressing plate 1 in the same way as when the cutting torque becomes excessive.
5, the force that forces the ball 14 to fit into the ball locking hole 17 is overcome by the force that pushes the ball 14 from the periphery of the ball locking hole 17, causing the ball 14 to lock as shown in FIG. Holder main body 1 (cylindrical main body 6) while pushing out from stop hole 17
moves forward in the axial direction relative to the spindle 7 while compressing the spring 16. That is,
It is also possible to prevent excessive axial compressive force from acting on the drill T, regardless of the cutting torque. Of course, in this case as well, the ball clutch 11 is switched to the non-transmission operating state, so the holder body 1
The transmission of cutting torque from the holder body 1 to the spindle 7 is also cut off, and the holder body 1 rotates idly relative to the spindle 7.

In any case, as mentioned above, the ball clutch 11
After switching to the non-transmission state or at the same time as the ball clutch 11 switches to the non-transmission state, the spindle 7 is moved relative to the holder body 1 (cylindrical body 6) against the spring 16. When the movable switch piece 27 of the switch means 26 moves backward, the movable switch piece 27 of the switch means 26 comes into contact with the contact surface 29 of the shank portion 3 at its tip contact portion 27a. The backward movement of the spindle 7 after this contact is performed by compressing the spring 28. When the tip contact portion 27a of the movable switch piece 27 and the contact surface 29 of the shank portion 3 contact each other in this way and the switch means 26 is closed, the shank portion 3, which is electrically insulated by the electrical insulation portion 10, The spindle 7 is electrically connected via the switching means 26.

By detecting electrical continuity between the shank portion 3 and the spindle 7 using the switch means 26, an abnormal situation in which the ball clutch 11 is activated is detected. It is possible to apply a detection method using a tool-work contact detection device as described in JP-A No. 61-214953.

That is, as shown in FIGS. 1 and 6, the sensor 30 loosely fits into the main shaft 2 and the sensor 30
The controller 31 connected to the controller 31 is used. The sensor 30 is composed of an excitation coil 32 and a detection coil 33, and the control device 31 includes a power supply section 34 that supplies a high frequency current to the excitation coil 32, and a power supply section 34 for obtaining a detection signal from the output signal of the detection coil 33. The detection section 35 is also provided.

However, when normal cutting and drilling work is being performed, the spindle 7 is held at the extended limit position, and the switch means 26 is in an open state as shown in FIG. is not electrically conductive. However, as described above, when the spindle 7 moves backward and the switch means 26 closes, and the spindle 7 and the shank portion 3 become electrically connected, the drill T and the conductive non-workpiece W
Because they are in the process of cutting, they are naturally in a contact and conductive state, so the main shaft 2, shank portion 3, switch means 26,
An electrical closed circuit 37 is formed that passes through the spindle 7, the drill T, the workpiece W, and the machine tool body 36 (see FIG. 6).

On the other hand, since a high frequency magnetic field is formed around the main shaft 2 by the high frequency current flowing through the excitation coil 32 of the sensor 30, a high frequency current is generated in the electrical closed circuit 37, and this high frequency current causes the sensing coil 33 to An induced current is induced and a detection signal is output. This detection signal is processed by the detection unit 35,
A detection signal 38 is output.

The detection signal 38 from the control device 31 is input to a controller that automatically controls the machine tool,
Machine tools can be automatically controlled according to a preset control program. For example, as mentioned above, the cause of the ball clutch 11 working is that the blade of the drill T is worn beyond the limit, and the cause of the overload can be resolved by once pulling out the drill T from the cutting hole. In this case, there is a possibility that chips may become clogged with chips wrapped around the drill T, so when the switch means 26 is closed and the detection signal 38 is output from the control device 31, the main shaft 2 is pulled out and the main shaft 2 is pulled out. A program is made to allow the drill T to escape from the cutting hole of the workpiece W, feed the spindle 2 again to restart the cutting action, and after restarting the cutting action, a similar overload occurs again and the detection signal 38 is output. If the reciprocating movement of the main spindle 2 is performed a set number of times by repeating the reciprocation of , it can be programmed to automatically replace the spare tool holder with a new drill T installed, and then resume the cutting action.

By performing automatic control using such a program, it is possible to automatically and rationally eliminate the cause of overload and replace the tool with a new one. However, when the switch means 26 is closed, the spindle The method for detecting electrical continuity between 7 and the shank portion 3 is not limited to the above-mentioned example method. For example, the method described in Japanese Patent Publication No. 48-40861 can also be applied.

When the holder body 1 is moved backward by the main shaft 2, the spindle 7 moves forward in the axial direction relative to the holder body 1 due to the biasing force of the spring 16 and reaches the limit position again, so that the ball pressing plate The ball 14, which is biased in the centrifugal direction by a spring 16 via a spring 15, is inserted into the ball locking hole 1 of the rotating holder main body 1 (cylindrical main body 6).
7 and returns to the transmission state again.

[Brief explanation of the drawing]

Figure 1 is a partially vertical side view, Figures 2 and 3 are cross-sectional views of the main parts, Figures 4 and 5 are vertical side views of the main parts explaining the action of the ball clutch, and Figure 6 is a cross-sectional view of the main parts. FIG. 2 is a schematic side view showing the entire machine tool and detection means. 1...Holder body, 2...Main shaft of machine tool,
3... Shock part, 4... Electrical insulating material, 6... Cylindrical body, 7... Spindle, 8a, 8b... Rotating bearing, 9... Tool chuck, 10... Electrical insulating part, 11... Ball Clutch, 12...Ball support plate, 13...Ball support groove, 14...Ball,
15... Ball pressing plate, 16... Compression coil spring, 17... Ball locking hole, 18... Transmission torque adjustment means, 19... Spring receiving plate, 20
... Long hole, 21 ... Thread groove machining peripheral surface, 22 ...
Annular groove, 23...adjustment ring, 26...switch means, 27...movable switch piece, 27a...tip contact portion, 28...spring, 29...contact surface,
30...sensor, 31...control device, 32...
Excitation coil, 33...detection coil, 34...power supply section, 35...detection section, 36...machine tool body, 3
7...Electrical closed circuit, 38...Detection signal.

Claims (1)

[Scope of utility model registration request] A spindle with a tool chuck at the tip is concentrically supported in a holder body that has a shank that attaches to a machine tool so that it can rotate around the axis and move within a certain range in the axial direction. Additionally, a clutch is interposed between the holder body and the spindle to bias and hold the spindle at the limit position and to slip at a certain torque or more, and the spindle and the shank are electrically connected. A rotary cutting tool holder comprising: an electrically insulating part; and a switch means that comes into contact with the spindle when the spindle moves backward from the extension position against a force to bring the spindle and the shank into electrical continuity.